Heredity

Results from genetic studies have shown that heredity (or the genetic material that we inherit through our parents and family) contributes to risk for developing both type 1 and type 2 diabetes. In type 2 diabetes, genetics plays a much stronger role than in type 1 diabetes.

A person with a close relative (a child or sibling) with type 1 diabetes has a greater chance of the developing the disease than someone without such a close family history (a 5% to 6% greater risk). However, type 1 diabetes often develops in people with no family history of the disease. This suggests that factors other than genetics probably play a strong role in increasing susceptibility for the disease.1

For type 2 diabetes, your risk for developing the disease is increased if you have a close family member (parent, sibling, or child) who has type 2 diabetes or a medical condition being overweight or obese, having lipid abnormalities, or high blood pressure. In fact, a person with a first-degree relative (parent, sibling, or child) with type 2 diabetes is 5 to 10 times more likely to develop the disease than someone without family history of the disease. Additionally, the risk for developing type 2 diabetes is highest among certain ethnic groups (people of Hispanic, African, or Asian descent).2

How do genes contribute to diabetes susceptiblity?

First, let’s define some terms. DNA (deoxyribonucleic acid) is the chemical structure (like a scaffold) that contains all of the genetic information used to make and maintain the body. Our DNA is made up of many individual genes (about 25,000 total). Each gene is a distinct portions of DNA that contains specific instructions for making some substance or structure that the body needs to function. Genes are packaged up in bundles called chromosomes. We have 23 pairs of chromosomes (46 total). Each pair of chromosomes contain genes that are responsible for determining the characteristics of our bodies.

Just as our DNA, which we inherit from our parents, determines whether we have blue or brown eyes or whether we are tall or short, it also influences the way our body functions, including how it produces and uses insulin to manage glucose and the way our immune system works (including the way it malfunctions, as in type 1 diabetes).

Genetic abnormalities linked to type 2 diabetes

Abnormalities in several genes have been linked to increased susceptibility to developing type 2 diabetes. These abnormalities are grouped in two areas:

  1. those that result in insulin resistance and
  2. those that result in decreased insulin secretion.

Insulin resistance. Insulin resistance, the inability of the body to respond normally to insulin, may result from abnormalities in genes link to obesity or genes that determine how our liver or other tissues respond to insulin.3

Low beta cell mass and abnormal beta cell function. Abnormalities in certain genes involved in the growth and function of beta cells have been linked to decreased insulin production. These defects, including low beta cell mass and problems with how the cells function, may explain why beta cells are unable to produce sufficient amounts of insulin in people with type 2 diabetes.3

Genetic abnormalities linked to type 1 diabetes

Researchers have identified several abnormalities in genes that increase susceptibility for developing type 1 diabetes. Included among these are gene variants involved in beta cell function (insulin production) and immune system function. Having one or more of these genes means that a person is at increased risk for the disease.4 Interestingly, several gene abnormalities that are linked to type 1 diabetes are also more common in people with other autoimmune diseases, including rheumatoid arthritis, celiac disease, and Crohn’s disease.5

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Written by: Jonathan Simmons | Last reviewed: May 2014.
View References
1. McCulloch DK. Patient information: Diabetes mellitus type 1: Overview (Beyond the Basics). Nathan DM, Mulder JE, eds. UptoDate. Wolters Kluwer Health. Accessed at: www.uptodate.com. 2013. -- 2. McCulloch DK. Patient information: Diabetes mellitus type 2: Overview (Beyond the Basics). Nathan DM, Mulder JE, eds. UptoDate. Wolters Kluwer Health. Accessed at: www.uptodate.com. 2013. -- 3. McCarthy MI. Genomics, Type 2 Diabetes, and Obesity. N Engl J Med 2010;363:2339-50. -- 4. Todd JA. Etiology of Type 1 Diabetes. Immunity 2010;32:457-67. -- 5. Pociot F, Akolkar B, Concannon P, et al. Genetics of Type 1 Diabetes: What's Next? Diabetes 2010;59:1561-71.